1. Field of the Invention
This invention relates to the field of downhole tools, measurement while drilling modules, centralizers and components.
2. Description of the Related Art
Downhole tools are used in drilling and production. Downhole tools include, among others, wireline logging tools, production logging tools, and tools that take measurements while drilling, such as measurement while drilling (MWD) tools, logging while drilling (LWD) tools, and survey while drilling (SWD) tools. Downhole tools are typically comprised of different modules coupled together. The coupling mechanism is sometimes integrated in the modules but typically the coupling mechanism is a separate device that also serves the function of centralizing the tool string in the drill collars or drill pipe. MWD tool strings are positioned downhole in a well to take measurements and convey the information to the surface. Examples of MWD modules include pulser modules, sensor modules, and battery modules, among others. A prior art MWD centralizer, shown in FIG. 1, is connected between two MWD modules to keep them centered in the well during the drilling process. The centralizer has electrical connectors at both ends to mate with matching electrical connectors on the ends of the MWD modules. Both the electrical connectors on the centralizer and the MWD modules have a combination of electrical pins and sockets for mating with each other. Different electrical connectors (that is, different electrical pin and socket configurations) are typically used on the two ends of the centralizer, but both ends of the centralizer have similar half-circular key configurations.
The industry standard is to have a four (4) electrical pin, six (6) socket electrical connector profile oriented vertically or at 90 degrees on the down-hole end of the centralizer, as shown on the right side of FIG. 1, and a six (6) electrical pin, four (4) socket electrical connector profile oriented at 45 degrees on the up-hole end of the centralizer, as shown on the left side of FIG. 1. The industry standard is to have a six (6) electrical pin, four (4) socket electrical connector profile oriented vertically or at 90 degrees on the up-hole end of the MWD module, and a four (4) pin, six (6) socket electrical connector profile oriented at 45 degrees on the down-hole end of the MWD module.
A tubular sleeve or pressure housing with internal threads at both ends is threadedly attached to both the MWD module and the centralizer to cover the electrical connection and protect it from the pressures in the well. Before the electrical connection can be made, the sleeve has to be threadedly attached to both the MWD module and the centralizer. The sleeve is usually first attached to the MWD module. After the sleeve is secured to the MWD module, the sleeve extends several inches past the electrical connector on the end of the MWD module, making the electrical connector difficult to access and see.
As shown in FIG. 2A, the electrical connectors on both ends of the centralizer are flush with the ends of the centralizer. Due to the configuration of the prior art centralizer, the threaded connection between the sleeve and the centralizer must be started and nearly completed before an electrical connection (e.g., pins of a connector electrically engaging the sockets of another connector) between the centralizer and the MWD module is made. The electrical connection is made “blind” in that the electrical connectors cannot be seen when the centralizer is being threadedly attached with the sleeve since the electrical connectors are covered by the sleeve. In addition, the electrical connection between the MWD module and the centralizer has to be made with more force than would otherwise be necessary since it must be made while threadingly attaching the sleeve with the centralizer.
The method and system of the past have several disadvantages. Since the key configurations on both ends of the centralizer are similar half-circular shapes, and since the electrical connector on the end of the MWD module is shielded by the sleeve and is difficult to see, it is common for the ends of the centralizer to be mistakenly reversed. An end of the centralizer with an incompatible electrical connector may be mistakenly threadedly attached with the sleeve of the MWD module, resulting in damage to the electrical pins of the electrical connectors, with the resulting costly repairs and delay. This is a common problem when dealing with components in the field where environmental conditions can be severe. Damage to the MWD module internal electronics may also occur.
Even if the correct end of centralizer is connected to the sleeve, the process is still time consuming. Initially, it takes time to insure that the centralizer is oriented correctly. Also, since the threaded physical connection between the centralizer and the sleeve has to be made before the electrical connection, the threaded connection has to be done slowly to insure that the electrical connectors, which cannot be seen due to the sleeve, align and mate. It is common for the threaded connection to be tightened, but the electrical connectors to not be electrically connected or coupled. In such a situation, the threaded connection has to be reversed a certain amount, and the inner housing of the centralizer that supports the electrical connector manually manipulated such as by twisting and pushing to insure the electrical connection is made, at which point the threaded connection has to be re-tightened. The determination of whether the electrical connection has been made properly is done by feel, which depends on the experience and training of the MWD operator.
It is also common to have the half-circular keys of the centralizer and MWD module almost aligned, and when the threaded connection begins to be made, the corners of both keys contact each other. When the threaded connection is continued to be made under such a condition, the corners of the electrical connectors often break. The disadvantages of the past have plagued the MWD industry for at least twenty years.
A need exists for a method and system to connect MWD modules with a device that prevents damage to the electrical connectors and saves time. A need also exists for a method and system to connect other downhole tools in addition to MWD modules.